Abstract: The oleander seed bug Caenocoris nerii (Germar, 1847) is a Mediterranean species associated primarily with Apocynaceae host plants that has been expanding its range northward in recent decades. We report new records of C. nerii in Bulgaria and discuss the distribution and the hosts of the species in the Black Sea region. Analysis of regional occurrence data revealed a clear northward range expansion since 2000, with very recent records from Croatia, Bosnia-Herzegovina, Serbia, and Romania. In Bulgaria, reproduction appears limited to areas where the primary host plant Periploca graeca occurs in suitable density, particularly in Black Sea wooded dunes and Flooded forests of Common alder (Alnus glutinosa). The timing and pattern of establishment suggest climate-mediated range expansion, as rising winter temperatures progressively remove thermal barriers that historically confined the species to the Mediterranean region. Our findings indicate that C. nerii is likely to continue spreading northward across the Danube River and Thracian lowland in areas with both suitable climatic conditions and host plant availability.
Keywords: climate change, Lygaeidae, milkweed bugs, Periploca graeca, range expansion
References [27]
Biserkov V., Gussev C., Popov V., Hibaum G., Roussakova V., Pandurski I., Uzunov Y., Dimitrov M., Tzonev R., Tsoneva S. (eds) 2011 Red Data Book of the Republic of Bulgaria. Volume 3. Natural habitats. BAS and MOEW, Sofia, 422 pp.
Cuesta Segura D., Baena Ruiz M., Mifsud D. 2010 New records of terrestrial bugs from the Maltese Islands with an updated list of Maltese Heteroptera (Insecta: Hemiptera). Bulletin of the Entomological society of Malta 3: 19–39.
Dawson N., Fischer J., Kuhn M., Pasotti A., Rouzaud D., Bruy A., Sutton T., Dobias M., Pellerin M., Rouault E., Olaya V., Blottiere P., Macho W., Blazek R., Sherman G., Sant-anna H., Cabieces J., Woodrow N., Bartoletti L. et al. 2025 qgis/QGIS: 3.44.0 (final-3_44_0). Zenodo. https://doi.org/10.5281/zenodo.15705458
European Environment Agency 2025 “Global and European temperatures – indicator assessment” online report, published 16 June 2025. https://www.eea.europa.eu/en/analysis/indicators/global-and-european-temperatures.
Evans D.L., Castoriades N., Badruddine H. 1986 Cardenolides in the Defense of Caenocoris nerii (Hemiptera). Oikos 46 (3): 325–329. https://doi.org/10.2307/3565830
GBIF.org 2025 GBIF Occurrence Download for Caenocoris nerii (Germar, 1847) (accessed 5 May 2025). GBIF.org. https://doi.org/10.15468/dl.cvu53n
Gianguzzi L., La Mantia A., Rocca R., Volpe A., Cambria S. 2025 Fragments of subdesert vegetation in the Mediterranean Region: the Periploca angustifolia maquis (Periplocion angustifoliae, Quercetea ilicis) in Sicily. Vegetation Ecology and Diversity 62: e175232. https://doi.org/10.3897/ved.175232
Glogov P.S., Georgieva M.L., Kachova V.G., Hinkov G. 2021 Two localities of Periploca graeca L. in the Danube islands Aydemir and Vetren (Ciocăneşti). Forest Science 1: 119–126.
Goula K. 2023 Apocynaceae: Periploca (ed. 1). In: Flora of Greece Editorial Committee (eds) Flora of Greece Vol. 1 Hellenic Botanical Society, Athens; Botanic Garden and Botanical Museum Berlin, Berlin, 1–5. https://doi.org/10.3372/fog.v1.apoc-peri.ed1
Josifov M. 1974 Die Heteropteren der bulgarischen Schwarzmeerküste. Bulletin de l’Institut de Zoologie et Musée 39: 5–25. (In Bulgarian)
Josifov M. 1999 Heteropterous insects in the Sandanski-Petrich Kettle, Southwestern Bulgaria. Historia naturalis bulgarica 10: 35–66.
Lodos N., Önder F., Pehlivan E., Atalay R., Erkin E., Karsavuran Y., Aksoy S. 1999 Faunistic studies on Lygaeidae (Heteroptera) of western Black Sea, Central Anatolia and Mediterranean regions of Turkey. Ege Üniversitesi Basımevi, Bornova, İzmir, 58 pp.
Martinović M., Dender D., Kulijer D., Koren T. 2023 New records of true bugs for the fauna of Croatia and Bosnia-Herzegovina. Entomologia Croatica 22: 37–43. https://doi.org/10.17971/ec.22.1.5
Peel M.C., Finlayson B.L., McMahon T.A. 2007 Updated world map of the Köppen-Geiger climate classification. Hydrology and Earth System Sciences 11 (5): 1633–1644. https://doi.org/10.5194/hess-11-1633-2007
Péricart J. 1998 Faune de France et régiones limitrophes. Vol. 84A. Hémiptères Lygaeidae Euro-Méditerranéens. Vol. 1. Fédération Française des Sociétés de Sciences Naturelles, Paris, 468 pp.
Péricart J. 2001 Family Lygaeidae Schilling, 1829 Seed-bugs. In: Aukema B., Rieger C. (eds) Catalogue of the Heteroptera of the Palaearctic Region Vol. 4 Netherlands Entomological Society, Amsterdam, 35–220.
Plants of the World Online 2025 Nerium oleander L. – distribution record. Royal Botanic Gardens, Kew.
Rabitsch W. 2008 The times they are a-changin’: driving forces of recent additions to the Heteroptera fauna of Austria. In: Grozeva S., Simov N. (eds) Advances in Heteroptera Research. Festschrift in Honour of 80th Anniversary of Michail Josifov. Pensoft Publishers, Sofia–Moscow, 309–326.
Radac I.A. 2022 Expansion of some native or alien species of seed beetles and true bugs in Romania (Insecta, Coleoptera, Heteroptera). Summary of the unpublished PhD Thesis. Babeș-Bolyai University, Faculty of Biology and Geology, Cluj-Napoca, Romania, 22 pp.
Simov N. 2011 True bugs collected on snow in Vitosha Mt., Bulgaria. A proposed method for investigation of flight activity and dispersal ability of Heteroptera (Hemiptera). Heteropterus Revista de Entomología 11 (2): 351–358.
Streito J.C., Labonne G., DuvaLLet G., DuSouLier F. 2015 Caenocoris nerii (Germar, 1847) à la conquête de la France méditerranéenne (Hemiptera Heteroptera Lygaeidae). L’Entomologiste 71 (2): 65–67.
Sweet II M.H. 2000 Chapter 6. Seed and Chinch Bugs (Lygaeoidea). In: Schaefer C.W., Panizzi A.R. (eds) Heteroptera of Economic Importance. CRC Press, Boca Raton, London, New York, Washington D.C., 143–243.
Thangavelu K. 1980 Influence of climate on populations of three milkweed bugs in South India. Proceedings – Animal Sciences, Springer 89: 579–586. https://doi.org/10.1007/BF03179058
Von Euw J., Reichstein T., Rothschild M. 1971 Heart poisons (cardiac glycosides) in the Lygaeid bugs Caenocoris nerii and Spilostethus pandurus. Insect Biochemistry 1 (4): 373–384. https://doi.org/10.1016/0020-1790(71)90002-3
Zito P., Sajeva M. 2012 Periploca laevigata subsp. angustifolia on Lampedusa Island. Asklepios 113: 22–27.
Supplementary materials [1]
01
Document title: Records of Caenocoris nerii in the Black Sea Region and adjacent Mediterranean locations
Kind of document: Comma-separated values (CSV)
MIME type: text/csv
Document name: 000616000482026-01.csv https://doi.org/10.48027/hnb.48.041/01
Additional information
Received: 29 January 2026 · Accepted: 4 March 2026
Editor: Mihail Kechev
Conflicts of interest:
No potential conflict of interest has been reported by the authors, reviewers, or subject editor. As members of the editorial board, Snejana Grozeva and Nikolay Simov withdrew from discussions and decisions on the manuscript.
Stoianova D., Karakicheva T., Grozeva S., Simov N. 2026 New records of the oleander seed bug Caenocoris nerii (Germar, 1847) (Insecta: Hemiptera) in Bulgaria and notes on its hosts in the Black Sea region. Historia naturalis bulgarica 48: 79–86.